Twenty years ago, Naylor led a study that sparked controversy by saying farmed fish and shellfish in some cases added pressure to ocean fisheries – instead of relieving it – because carnivorous farm-raised species required large amounts of wild fish for feed. The paper, also published in Nature, prompted news stories and academic research questioning whether aquaculture was more of an environmental problem than a solution.
Environmental groups applauded the study’s focus on aquaculture’s marine ecosystem impacts, while the industry pointed to hopeful developments that were largely ignored, such as ongoing improvements in fish nutrition.
Since then, the volume of global aquaculture production has tripled. In the new paper, aquaculture specialists and scientists from Asia, Europe, South America and the United States assessed the state of the industry by synthesising hundreds of studies conducted over the past two decades on issues ranging from value chain developments in freshwater aquaculture to the use of wild fish in feeds to seaweed market challenges.
Their analysis considered key challenges and uncertainties, such as climate change’s impact on the industry, low-income producers’ adoption of sustainable seafood certification programmes and shellfish and seaweed farmers’ ability to profit from providing ecosystem services, such as carbon capture.
Among the findings, freshwater aquaculture - comprising nearly 150 species of fish, shellfish and plants - accounts for 75% of farmed aquatic food consumed directly by humans.
Professor David Little of the University of Stirling’s Institute for Aquaculture, said: “Most aquaculture is about fish people can afford to eat – and most of the farming of aquatic animals happening in Asian countries stays in those countries. It’s having an important impact on food security and rural livelihoods.”
Other regions, including Africa, are increasingly benefitting from the introduction of freshwater aquaculture. But while small freshwater farms are on the rise around the world, there is little oversight of their practices.
The researchers also found that the production of high-value shrimp, salmon and other marine fish rose rapidly, contributing to a significant rise in the share of global fishmeal and fish oil used by aquaculture. Yet, the ratio of wild fish input per fed fish output has dropped almost seven-fold since 1997.
“We have been successful in converting carnivorous fish, such as salmon and trout, largely into vegetarians,” said study co-author Ronald Hardy of the Aquaculture Research Institute at the University of Idaho.
In the study, the researchers call for better management of antimicrobial use in fish farming to limit the development of drug-resistant microbes that threaten both fish and human health, and regulation of marine farm sites.
They also recommended incentives for sustainably designed systems to prevent cross-contamination between fish waste and surrounding waters, and a food systems approach to governance that considers nutrition, equity, justice and environmental outcomes and trade-offs across land and sea.
The study was funded by Stanford’s Center on Food Security and the Environment. Other co-authors include Alejandro Buschmann (the Universidad de Los Lagos, Chile), Simon Bush (Wageningen University, Netherlands), Ling Cao (Shanghai Jiao Tong University, China), Jane Lubchenco (Oregon State University), Sandra Shumway (University of Connecticut) and Max Troell (the Beijer Institute and Stockholm University, Sweden).
The researchers will share observations from their analysis in a related seminar, ‘Is Aquaculture Breaking Into the Global Food System?’ at 1pm on Tuesday, 30th March.